Figure 2.(a) Schematics of the LSM interferometer, with the target moving forward (red arrow) or backward (blue arrow) with respect to the laser source. (b) Experimental oscilloscope waveforms obtained for different values of the feedback parameter C in presence …Several benefits derive from the LSM scheme. First, the optical alignment procedure is not so critical as in external interferometers, since there is only one measurement arm, the reference arm provided by the laser itself. Second, the reference arm is self-stabilized once the driving current and the heat sink temperature of the laser source are kept constant. Third, the output signal can be detected by a photodiode placed anywhere along the optical path.

The geometry of the setup can be optimized if the signal is detected by means of the photodiode integrated into most commercial laser packages for power monitoring, which allows the laser to be used as source and detector at the same time. The basic setup, sketched in Figure 2(a), is thereby made of only a laser source, a collimating lens, a remote target, and a neutral attenuator if any adjustment of the feedback power is required. Actually, this setup can be considered as an evolution of the Michelson interferometer with the reference arm folded on itself toward the laser source, whose front facet serves as the beam splitter.Fourth, the feedback regime, i.e. the relative amount of light coupled back into the laser, affects the characteristics of the output signal in a non-linear way, allowing for the identification of the sign of the displacement by means of a single quadrature.

A useful classification of the feedback regimes for metrological purposes can be performed by adopting the C-value as selective parameter [13], where C is the feedback parameter [14] defined as follows:C=?R3R2(1?R2)1+��2xl?neff(1)Expression (1) depends on a combination of laser dependent parameters (R2 is power reflection coefficient Anacetrapib of the front laser facet, l is the laser cavity length, neff is the effective refractive index of the active medium, �� is the linewidth enhancement factor) and system adjustable parameters (R3 is the power reflection coefficient of the target, also i
The term ��Ubiquitous Sensor Networks�� (USN) is used to describe networks of smart sensor nodes capable of communicating wirelessly, and possessing limited computing power and storage capacity. USN can be used in a wide range of civilian and military fields, including environment and habitat monitoring, real-time healthcare, landmine detection, intelligent transport systems and so on [1].